mysterious illness affecting thousands of pets. The fda is reporting that a sickness caused by jerky treats has killed nearly 600 dogs. And sickened 3,600 dogs, as welt as cats. The fda has not identified any brands, and there's no recall yet. Confusing situation for pet owners. Dr. Richard besser is here with this. This is a really big mystery. It started in 2007. As you said, 580 dogs have died and some cats. 3,600 have been sickened. It's from chicken, duck and sweet potato jerky. The food and drug administration are responsible for pet food. They've been testing for bacteria, for pesticides, for metal, for toxins. They've come up empty. Now, they're asking all veterinarians across the country, be on the lookout for this. Contact them if they see any dogs who have an illness that could be this. What about symptoms? What you're going to see is their dog will be off their appeti appetite. They have vomiting. It can progress to kidney failure. Many recover. But many die. What is your advice to pet owners? These are treats. They're treats. They don't have to be part of the diet. There's nothing you can see on the label because they're not required to label what country they come from. If you're concerned about this, you don't have to give your pet a treat. They don't need a jerky treat. They're not going to give the brands or anything like that. There's no recall because they haven't linked it to any particular brand. Unless they do that, they can't issue a recall. Buyer beware. We're going to turn to high

This transcript has been automatically generated and may not be 100% accurate.

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